In a low-risk pregnant patient at 21 weeks' gestation, ultrasound revealed shortening of fetal long bones compatible with achondroplasia. Funipuncture was performed and DNA analysis of fetal blood demonstrated the presence of the GR380R fibroblast growth factor receptor 3 (FGFR3), which is specifically associated with achondroplasia. After termination of the pregnancy, necropsy confirmed the prenatal diagnosis. A certain sonographic diagnosis of fetal de novo achondroplasia is rarely possible prior to viability. The specificity of the FGFR3 causative mutation has added a new diagnostic option which can be applied prenatally for diagnostic validation.